Polyethylene terephthalate (PET) is increasingly used as a barrier material in place of Nylon (PA) or EVOH, or in combination with EVOH, to reduce the overall cost of packaging structures. Typically, the structures, such as PET/tie-layer/PE or PE/tie-layer/EVOH/tie-layer/PET are often extruded into films (see, for example, FIG. 1), ranging from 250 to 1250 microns, and thermoformed for packaging applications. Such film structures can also be typically blown into flexible films for packaging. Some conventional tie-layer solutions include maleic anhydride modified ethylene methylacrylate polymers, and maleic anhydride modified ethylene vinyl acetate polymers. The tie layer requirements have been becoming more demanding, requiring higher adhesion properties. However these current tie-layer materials are often disadvantageous because of negative taste and odor properties and/or insufficient thermal stability at high processing temperatures (≥225° C.) Thus, there is a need for new film compositions that contain tie-layers that have improved adhesion to polyesters, good high temperature processibility and low taste and odor levels.
U.S. Pat. No. 6,027,776 discloses a multilayer film that includes the following: a) an interior layer of homogeneous ethylene/alpha-olefin copolymer having a density ranging from about 0.89 to about 0.92 grams per cubic centimeter; b) a first exterior layer of a material selected from the group consisting of homopolymer or copolymer of polypropylene, a blend of homopolymer or copolymer of polypropylene and elastomer, high density polyethylene, and copolyester; and c) a second exterior layer of a material selected from the group consisting of polyamide, copolyamide, polyester, copolyester, high density polyethylene, polypropylene, propylene/ethylene copolymer, and polycarbonate. A first adhesive layer is present between the interior layer and the first exterior layer, and a second adhesive layer is present between the interior layer and the second exterior layer.
U.S. Pat. No. 6,183,863 discloses an adhesive ethylene copolymer resin blend of a modified ethylene/α-olefin copolymer, obtained by graft-modifying an unmodified linear ethylene/α-olefin copolymer with an unsaturated carboxylic acid or its derivative, or the unmodified ethylene/α-olefin copolymer and the modified ethylene/α-olefin copolymer, and an olefin elastomer. The linear ethylene/α-olefin copolymer is prepared using an olefin polymerization catalyst including a Group IV transition metal compound (a) containing a ligand having cyclopentadienyl skeleton and an organoaluminum oxy-compound. The adhesive ethylene copolymer composition can be used as a layer, in a laminate, with a layer of a polar material or a layer of a metal. The polar material can be an ethylene/vinyl alcohol copolymer, a polyamide, or a polyester. See also U.S. Pat. No. 6,656,601.
U.S. Publication 2011/0297212 discloses a laminated film having a substrate, and a bonding layer of ethylene polymer on one major surface of the substrate. The bonding layer is placed directly on the substrate, or there is a primer layer between the substrate and bonding layer.
Additional film compositions are disclosed in the following references: U.S. Pat. Nos. 4,639,398; 5,837,358; 6,274,246; 6,663,974; U.S. Publication Nos. 2002/0055006, 2007/0254118, 2008/0197540, 2008/0274328, 2008/0274314, 2010/0029827; International Publication Nos. WO 2008/079784, WO 2010/042334, WO 2010/042335; Japanese Patent References: JP10034836A (Abstract), JP03-106647A (Abstract), JP02551977B2 (Abstract), JP0307557B2 (Abstract), JP7103278B2 (Abstract), JP64-045445 (Abstract), JP2009-019063 (Abstract), JP01-317756 (Abstract), JP06-126882 (Abstract); Journal References: De Gooijer, J. M.; Scheltus, M. and Koning, C. E.; Polym. Eng. Sci. 41, 2001, 86-94; Pietrasanta, Y.; Robin, J. J.; Tones, N.; Boutevin, B.; Macromol. Chem. Phys. 200, 1999, 142-149; Becker, P. and Kiang, W.; ANTEC, 1991, 1389-94; and Durgun, H; Bayram, G. J. Adhesion Sci. Technol., 19, 2005, 407-425.
However, as discussed above, there remains a need for new multilayer film configurations that contain tie-layers compositions that have improved adhesion to polyesters. These needs and others have been met by the following invention.